1. Field of the Invention
The present invention relates generally to devices for transporting portable articles and may be used with particular advantage in hospitals, hotels, schools, and the like. More particularly, the present invention relates to a modular, knock-down utility cart that is easy to manufacture, to ship in knocked down condition from the point of manufacture to the point of use, and that can be easily assembled and later disassembled for compact storage. Still further, this modular utility cart incorporates improved structures for mounting intermediate shelves and a top shelf on corner supporting posts.
2. Description of the Prior Art
Utility carts of the type described above are ordinarily provided with four casters. They may include four corner posts, a handle at one or both ends of the cart, and two or more shelves such as a top and an intermediate shelf supported by the corner posts. Such carts have been manufactured as unitary welded or otherwise assembled structures or in knock-down modular form.
One problem with unitary utility carts employing, for example, welded construction, is that they are expensive to store and ship because of their size. Additionally, they may not be disassembled for compact storage when not in use.
The advent of knock-down utility carts constitutes a substantial improvement over carts having unitary construction. One such knock-down utility cart is described and illustrated in U.S. Pat. No. 4,595,107 (Welsch) assigned to the Assignee of the subject invention. This device generally incorporates four-corner posts, each of which is provided with a caster at its bottom and two or more shelves are mounted on the corner posts using the InterMetro Industries SUPER ERECTA modular shelving system. The device also incorporates an improved modular handle arrangement. U.S. Pat. Nos. 3,424,111 (Maslow) and 3,757,705 (Maslow), also assigned to the Assignee of the subject invention, describe the SUPER ERECTA system, which generally incorporates four right cylindrical corner posts each formed with a plurality of regularly spaced angular grooves along the axis of the post. Each shelf is provided with a frustoconical collar that receives a similar frustoconical sleeve which in turn embraces the post. Downward movement of the shelf causes the collar and sleeve to interengage thereby inwardly compressing the sleeve against the post. The sleeve shown in U.S. Pat. No. 3,757,705 includes an annular outwardly projecting flange at its bottom edge which is said to limit downward movement of a collar on the sleeve. However, this exposed flange has a tendency to collect contaminants and, therefore, may become unsanitary.
Further, in shelving system and particularly utility cart applications, it may be desirable to make shelves out of plastic material such as structural foam. However, because of the inherent nature of such material, they exhibit plastic deformation or tend to "creep". If plastic is used in shelving in the SUPER ERECTA system a frustoconical collar formed directly in the plastic shelf has a tendency to expand radially outwardly as it engages the outer frustoconical surface of a sleeve. Thus, the collar in the shelf may eventually override the sleeve in such a way as to cause the structural integrity of the system significantly to deteriorate.
Further, when mounting a top shelf on four corner posts using the SUPER ERECTA shelf system in utility cart applications, provision should be made to resist disassembly of the top shelf from the posts by upward movement that might result if an operator lifts the top shelf, for example, to move the cart over an obstacle.